// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef NET_PROXY_PROXY_CONFIG_SERVICE_H_
#define NET_PROXY_PROXY_CONFIG_SERVICE_H_

#include "net/base/net_export.h"

namespace net {

class ProxyConfig;

// Service for watching when the proxy settings have changed.
class NET_EXPORT ProxyConfigService {
public:
    // Indicates whether proxy configuration is valid, and if not, why.
    enum ConfigAvailability {
        // Configuration is pending, observers will be notified later.
        CONFIG_PENDING,
        // Configuration is present and valid.
        CONFIG_VALID,
        // No configuration is set.
        CONFIG_UNSET
    };

    // Observer for being notified when the proxy settings have changed.
    class NET_EXPORT Observer {
    public:
        virtual ~Observer() { }
        // Notification callback that should be invoked by ProxyConfigService
        // implementors whenever the configuration changes. |availability| indicates
        // the new availability status and can be CONFIG_UNSET or CONFIG_VALID (in
        // which case |config| contains the configuration). Implementors must not
        // pass CONFIG_PENDING.
        virtual void OnProxyConfigChanged(const ProxyConfig& config,
            ConfigAvailability availability)
            = 0;
    };

    virtual ~ProxyConfigService() { }

    // Adds/Removes an observer that will be called whenever the proxy
    // configuration has changed.
    virtual void AddObserver(Observer* observer) = 0;
    virtual void RemoveObserver(Observer* observer) = 0;

    // Gets the most recent availability status. If a configuration is present,
    // the proxy configuration is written to |config| and CONFIG_VALID is
    // returned. Returns CONFIG_PENDING if it is not available yet. In this case,
    // it is guaranteed that subscribed observers will be notified of a change at
    // some point in the future once the configuration is available.
    // Note that to avoid re-entrancy problems, implementations should not
    // dispatch any change notifications from within this function.
    virtual ConfigAvailability GetLatestProxyConfig(ProxyConfig* config) = 0;

    // ProxyService will call this periodically during periods of activity.
    // It can be used as a signal for polling-based implementations.
    //
    // Note that this is purely used as an optimization -- polling
    // implementations could simply set a global timer that goes off every
    // X seconds at which point they check for changes. However that has
    // the disadvantage of doing continuous work even during idle periods.
    virtual void OnLazyPoll() { }
};

} // namespace net

#endif // NET_PROXY_PROXY_CONFIG_SERVICE_H_
